By MICHAEL GRACZYK

HOUSTON (AP) – Larry Gonzales was emerging from his Garda Cash Logistics armored truck to refill an ATM at a Houston-area Chase Bank in October 2013 when a man behind him demanded money.

“People joke around with us,” said Gonzales. “I didn’t think this dude was actually serious. Next thing, I get shot in the back. Then I knew this was for real.” The 28-year-old was shot six times and, despite multiple surgeries, still has a “lucky” bullet lodged in his chest.

Gonzales’ case is not unique. Federal statistics indicate Texas’ largest city has become a hub for bank and armored-truck hold-ups, but authorities are puzzled as to why.

“Clearly that is an issue that concerns us,” says Carlos Barron, assistant special agent in charge of the Houston FBI office who oversees the local bureau’s Violent Crimes Task Force.

Eleven armored trucks were robbed in Houston in 2013 and another eight last year, accounting for 20 percent of all such heists in the U.S. In 2013, 120 banks were robbed around Houston – one every three days. Last year the number dipped slightly to 100, while nearly 4,000 banks, savings and loans and credit unions were held up nationwide, according to FBI statistics.

While authorities say the raw numbers for Houston are comparable to other large U.S. metropolitan areas, 40 percent of the bank holdups in the city last year were takeover robberies, in which two or more armed attackers control the bank by holding employees and customers at gunpoint. The FBI says Houston has more takeover bank robberies than any other city in the country.

The numbers have authorities guessing.

“We’ve looked at the data, studied the data,” Barron said. “I don’t think we’ve extracted any trends.”

During a recent visit to Houston, FBI Director James Comey offered what he described as “uneducated guesses” to explain the concentration of heists.

He speculated that Houston’s “breathtakingly large surface area” allowed robbers to easily hide. The eight-county area covers 8,778 square miles, slightly smaller than Massachusetts.

He also suggested some crimes simply become fashionable.

“Bad fads can be stamped out and that’s what we’re going to try to do,” Comey said.

James Mann, retired chief psychologist at the Federal Bureau of Prisons, said copycats are rare but that young offenders “tend to do some things that they see other people doing.”

Usually bank robbers work alone, but Mann said it looks like the crimes in Houston “are much more organized and premeditated.”

Barron agreed the Houston-area robberies could be gang-related, but said no specific gang seemed to be responsible.

It was the boldness of a Brinks armored car holdup in broad daylight on Feb. 12 in Houston’s Galleria area that particularly caught investigators’ attention.

“That’s like saying 2 p.m. on Park Avenue (in New York City),” Barron said.

Brinks employee Alvin Kinney was ambushed and shot to death by three people wearing body armor and masks. His partner exchanged shots with the gunmen, who grabbed bags of cash and drove off in a stolen pickup truck.

Deaths in armored truck and bank robberies are rare. Of 24 armored carrier robberies nationwide in 2014, two people – both of them perpetrators – were killed, FBI statistics show. Similarly, of 3,961 bank robberies last year, 13 fatalities included 10 robbers, two employees and one customer.

Up to $100,000 in rewards have been offered for information leading to an arrest in Kinney’s unsolved case, one of at least two armored car holdups in Houston or surrounding Harris County this year. At least 31 bank robberies already have occurred, 17 of them takeover robberies.

Law enforcement has had some success in catching up with the Houston robbers. In April, 22 people were arrested on federal charges in bank robberies from 2013 to present, and two Houston men who prosecutors say are responsible for 17 bank robberies were sentenced to up to 20 years in prison.

Gonzales, 28, remembers pulling his weapon after he had been shot and fallen to the ground.

“I saw the guy who shot me, he was about to run up and I guess to finish me off,” he said. “That’s when I started shooting back.” The robbers took gunfire from Gonzales’ partner and fled, empty handed.

In May, Gonzales watched as his attackers were sentenced. William Williams, 29, pleaded guilty to four charges, including shooting Gonzales, and was sentenced to 30 years in a federal prison. Prosecutors said he’d been involved in at least one other armored car holdup in 2013.

“What’s sad is they’re my age, pretty much the best years of your life,” he said. “They pretty much blew it.”